For completeness, I have the answer from the Canadian Consulate; since I can't find it anywhere online here it is:
Transit Without Visa Program for Nationals of Indonesia, Philippines, Taiwan and Thailand
Citizenship and Immigration Canada, in co-operation with the Vancouver International Airport Authority and various domestic and foreign air carries, has introduced a pilot Transit Without Visa program at Vancouver International Airport (VIA) to reduce the inconvenience and cost of travel through Canada.
Effective June 28, 2002 , nationals of Indonesia, Philippines, Taiwan and Thailand, subject to certain conditions, are allowed to transit VIA to and from the United States without the need to obtain a Canadian temporary resident visa.
Eligibility Requirements for Travellers
Nationals of Indonesia, Philippines, Taiwan and Thailand transiting Canada at VIA
to the United States must have in their possession a valid and subsisting U.S. visa to enter the United States and must:
- be ticketed or arrive on a carrier that has access to U.S. intransit preclearance inspection without first having to be examined by a Canadian immigration officer; or,
- arrive and leave Canada on a flight that will be cleared by U.S. inspection agencies upon arrival in the United States.
Nationals of Indonesia, Philippines, Taiwan and Thailand transiting Canada
from the United States must:
- at the time of their arrival in the U.S. , have had in their possession a valid U.S. visa to enter the United States ( persons allowed entry to the U.S. under the U.S. TRWOV or Visa Waiver programs are not eligible for this program );
- have been lawfully admitted to the U.S. and have hot overstayed the period of time they were authorized to remain in the United States;
- not be deported or otherwise removed from the United States unless, having been refused admission to the U.S. after transiting Canada on a flight that was not cleared by U.S. preclearance inspectors at VIA, are removed from the U.S. within seven days of their arrival; and,
- arrive at VIA on a flight directly from the United States and be destined to a third country to which they are admissible.
Eligible person must have outbound air transportation booked for departure from VIA within 24 hours of arrival in Canada . TWOV passengers may be boarded on any outbound flight from VIA regardless of whether or not the carrier is a signatory to the TWOV program.
The following transportation companies are eligible to carry TWOV passengers to Canada:
Air Canada
Alaska Airlines
American Airlines
Cathay Pacific Airways
China Airlines
Philippines Airlines
To determine whether your proposed flights meet the above requirement, we recommend you contact your airline.
